The present invention relates to a transmission unit to be installed in a hybrid vehicle combining an engine and a motor, to obtain a driving force.
With improved fuel economy and lower emissions, hybrid vehicles benefit conservation of global environment and savings of limited resources. In a hybrid vehicle, a motor is arranged in series or parallel to an engine to assist the engine and to serve as a generator for converting kinetic energy of the vehicle to electrical energy on deceleration.
A published Japanese patent application Publication (Kokai) No. 9(1997)-329228 shows a conventional transmission having a planetary gear system. This transmission is designed to add a motor without changing the basic layout of a conventional transmission to reduce the manufacturing cost. The transmission of this example includes, as shown in FIG. 7A, a torque converter chamber 101 defined by a first housing 113 and a first partition 116, a planetary gear chamber 102 defined by a second housing 114, the first partition 116 and a second partition 117, and a transmission chamber 103 defined by a third housing 115 and the second partition 117. Rotation from the engine is inputted to a torque converter 110 in the torque converter chamber 101, the output from the torque converter 110 is inputted:the planetary gear system in the planetary gear chamber 102 and further to a transmission 112 in the transmission chamber 103.
When a motor is disposed in the planetary gear chamber without changing the basic layout, a water jacket formed around the motor is effective to cool the motor having the coil heated by repetition of drive and generation.
A published Japanese patent application Publication (Kokai) No. 2000-9213 shows an apparatus having an electromagnetic clutch in the torque converter chamber 101 and a motor in the planetary gear chamber 102, as shown in FIG. 7A.
However, the space for the water jacket is limited because, as shown in FIGS. 7A and 7B, a transmission input shaft 120, a driven shaft 121, an idler shaft 123 and a differential 124 are arranged with proper distances between adjacent axes. FIG. 8 shows a front view of the housing of the transmission unit of FIG. 7B. As shown in FIG. 8, a motor receiving: portion 231 for receiving the motor is surrounded by a driven pulley receiving portion 232 for a driven pulley, a differential receiving portion 233 for a differential, and a parking support receiving portion 234 for a parking pole support.
An object of the present invention is to provide a transmission unit for a hybrid vehicle, having a water jacket to cool a motor efficiently. Another object is to provide a transmission unit in which a water jacket is formed compactly without the need for changing a layout of a conventional design. Still another object is to provide an annular water jacket designed to improve the cooling performance by holding the flow rate uniform all round the circumference.
According to the present invention, a transmission unit for a hybrid vehicle, the transmission unit comprises a unit housing which comprises;
a first section (such as an item 42) defining a clutch chamber for containing an electromagnetic clutch;
a second section (such as an item 41a) defining a transmission chamber for containing a transmission; and
a third -section (such as an item 41b) defining a motor chamber for containing a motor comprising a rotor and a stator, and a water jacket for circulation of water to cool the stator.
The water jacket comprises an annular passage extending around the motor chamber, and comprising a water inlet for introducing the coolant into the annular passage, a water outlet for discharging the coolant from the annular passage, and a depressed or uneven portion which is depressed to form a space for receiving an adjacent component of the transmission unit, and which has a cross sectional shape varied gradually so that a flow sectional area remains uniform.